3d printing ink containing a cyclopolymerizable monomer

ABSTRACT

In one aspect, inks for use with a three-dimensional (3D) printing system are described herein. In some embodiments, an ink described herein comprise 10-70 wt. % or 20-40 wt. % of a cyclopolymerizable monomer, based on the total weight of the ink. The cyclopolymerizable monomer comprises an acrylate moiety and an ethenyl or ethynyl moiety, and the α-carbon of the acrylate moiety and the α-carbon of the ethenyl or ethynyl moiety may have a 1,5-, 1,6-, 1,7-, or 1,8-relationship. Additionally, an ink described herein can have a viscosity of 1600 centipoise (cP) or less at 30° C., or of 500 cP or less at 30° C. and can be used to print a desired 3D article having mechanical properties similar to those of articles formed from thermoplastic materials.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority pursuant to 35 U.S.C. § 119(e) to U.S.Provisional Patent Application No. 62/453,169 filed Feb. 1, 2017, and toU.S. Provisional Patent Application No. 62/573,756 filed Oct. 18, 2017,each of which is hereby incorporated by reference in its entirety.

FIELD

The present invention relates to inks and, in particular, inkscomprising a cyclopolymerizable monomer for use with three-dimensional(3D) printing systems.

BACKGROUND

Some commercially available 3D printers, such as the Projet™ 3D Printersmanufactured by 3D Systems of Rock Hill, S.C., use inks, which are alsoknown as build materials, that are jetted through a print head as aliquid to form various 3D objects, articles, or parts. Other 3D printingsystems also use an ink that is jetted through a print head or otherwisedispensed onto a substrate. In some instances, the ink is solid atambient temperatures and converts to liquid at elevated jettingtemperatures. In other instances, the ink is liquid at ambienttemperatures. Moreover, in some cases, the ink can be cured followingdispensing and/or deposition of the ink onto the substrate.

Other 3D printers form 3D articles from a reservoir, vat, or containerof a fluid ink or build material or a powdered ink or build material. Insome cases, a binder material or a laser or other source of energy isused to selectively solidify or consolidate layers of the ink or buildmaterial in a stepwise fashion to provide the 3D article.

Inks for 3D printing systems can be used to form a variety of articlesfor a variety of applications, including in a manner describedhereinabove. However, there is a very high demand for inks that can formarticles having superior mechanical properties. For example, there is ahigh demand for inks that can form articles with mechanical propertiessimilar to articles formed from thermoplastic materials.

Prior inks for 3D printing systems that contain acrylates can be used toprint articles with very good resolution, but often the resultingarticles are rigid, brittle, or flexible but easily breakable. Theimpact resistance of such articles can be especially low compared tosome other articles. Therefore, there exists a need for improvedacrylate-containing inks for 3D printing that form articles havingimproved mechanical properties. Particularly, a need exists foracrylate-containing inks that produce articles having mechanicalproperties more like those exhibited by articles formed fromthermoplastic materials.

SUMMARY

In one aspect, inks for use with a 3D printer are described herein,which in some embodiments, may offer one or more advantages over prioracrylate-containing inks. For example, inks described herein can be usedto print articles with improved mechanical properties, includingimproved impact resistance, compared to those printed with prioracrylate-containing inks. In some embodiments, articles printed usinginks described herein also have improved tensile modulus, tensilestrength, and/or elongation, compared to articles printed using prioracrylate-containing inks. Additionally, in some cases, inks describedherein have reduced viscosity compared to prior acrylate-containinginks. As a result, inks described herein can be used in a variety ofdifferent 3D printers, such as those based on Stereolithography (SLA),Digital Light Processing (DLP), and Multi-Jet Printing (MJP). Further,due at least in part to their reduced viscosity, inks described hereincan also print easily and quickly.

In some embodiments, an ink for use in a 3D printing system describedherein comprises 10-70 wt. % or 20-40 wt. % of a cyclopolymerizablemonomer, based on the total weight of the ink. The cyclopolymerizablemonomer comprises an acrylate moiety and an ethenyl or ethynyl moiety,and the α-carbon of the acrylate moiety and the α-carbon of the ethenylor ethynyl moiety may have a 1,5-, 1,6-, 1,7-, or 1,8-relationship. Insome cases, the cyclopolymerizable monomer may be a monomer having thestructure of Formula (I):

wherein X is O, S, NH, NR₅, or CR₅R₆;R₁ is H or a hydrocarbon group having 1-10 carbon atoms;R₂ is a hydrocarbon group having 1-4 carbon atoms;R₃ is a hydrocarbon group having 1-4 carbon atoms;R₄ is HC═CH₂ or C≡CH;R₅ is a hydrocarbon group having 1-4 carbon atoms; andR₆ is a hydrocarbon group having 1-4 carbon atoms.Additionally, the total number of carbon atoms of R₂ and R₃ does notexceed 5. For example, in some instances, a cyclopolymerizable monomerrepresented by Formula (I) has the more specific structure of Formula(II):

In addition to the above-described cyclopolymerizable monomer, an inkdescribed herein, in some cases, may further comprise up to 80 wt. % ofoligomeric curable material and/or up to 80 wt. % of additionalmonomeric curable material, based on the total weight of the ink. An inkdescribed herein may also comprise at least one photoinitiator, at leastone colorant, or both. Additionally, an ink described herein maycomprise one or more additives selected from the group consisting ofinhibitors and stabilizing agents. Further, it is also possible for anink described herein to include up to 15 wt. % or up to 10 wt. % ofnon-curable polymer or oligomer.

Moreover, an ink described herein, in some instances, has a viscosity of1600 centipoise (cP) or less at 30° C., or of 500 cP or less at 30° C.

In another aspect, methods of printing a 3D article using any of theforegoing inks are described herein. In some cases, for instance, such amethod comprises selectively depositing layers of an ink in a fluidstate onto a substrate. Moreover, in some embodiments, the ink ispartially cured prior to completion of deposition of all layers of theink. Partially curing, in some embodiments, primarily comprisespolymerizing the acrylate moiety of the cyclopolymerizable monomerand/or other acrylate-containing species of the ink via acrylatepolymerization. Additionally, in some cases, following the completion ofdeposition of all layers of the ink, the ink is post-cured. Post-curing,in some embodiments, primarily comprises cyclopolymerizing the acrylatemoiety and the ethenyl or ethynyl moiety of the cyclopolymerizablemonomer of the ink. Further, in some cases, partially curing andpost-curing each comprise photocuring, i.e., curing with a light source.Moreover, in some embodiments, a light source used for post-curing has ahigher energy than a light source use for partially curing. For example,in some cases, the light source used for post-curing may be a Hg lampand the light source used for partially curing may be a Xe arc lamp.

In another method of printing a 3D article described herein, the methodcomprises retaining an ink described herein in a fluid state in acontainer; and selectively applying energy to the ink in the containerto solidify at least a portion of a first fluid layer of the ink,thereby forming a first solidified layer that defines a firstcross-section of the article. Such a method can further comprise raisingor lowering the first solidified layer to provide a second fluid layerof the ink at a surface of the fluid ink in the container; andselectively applying energy to the ink in the container to solidify atleast a portion of the second fluid layer of the ink, thereby forming asecond solidified layer that defines a second cross-section of thearticle, the first cross-section and the second cross-section beingbonded to one another in a z-direction. As described furtherhereinbelow, the foregoing steps may be repeated any desired number oftimes needed to complete the 3D article. Moreover, in some cases,selectively applying energy to the ink in the container comprisespartially curing the ink. Partially curing the ink may primarilycomprise polymerizing the acrylate moiety of the cyclopolymerizablemonomer and/or one or other additional acrylate-containing species ofthe ink via acrylate polymerization. In addition, in some instances, amethod described further comprises post-curing the 3D article followingits formation. Post-curing, in some cases, may primarily comprisecyclopolymerizing the acrylate moiety and the ethenyl or ethynyl moietyof the cyclopolymerizable monomer of the ink. Further, partially curingand post curing each may comprise photocuring. In some such instances, alight source used for post-curing may have a higher energy than a lightsource used for partially curing. For example, a Hg lamp may be used forpost-curing, and a Xe arc lamp may be used for partially curing.

In still another aspect, printed 3D articles are described herein. Inparticular, 3D articles formed from an ink and/or using a methoddescribed hereinabove are disclosed. Such printed 3D articles, in somecases, have superior mechanical properties compared to some other 3Darticles, as described further herein. For instance, in someembodiments, a 3D article described herein has one or more mechanicalproperties similar to those exhibited by thermoplastic molded articles.

These and other embodiments are described in greater detail in thedetailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates polymerization of a cyclopolymerizable monomeraccording to some embodiments described herein.

DETAILED DESCRIPTION

Embodiments described herein can be understood more readily by referenceto the following detailed description and examples. Elements, apparatusand methods described herein, however, are not limited to the specificembodiments presented in the detailed description and examples. Itshould be recognized that these embodiments are merely illustrative ofthe principles of the present disclosure. Numerous modifications andadaptations will be readily apparent to those of skill in the artwithout departing from the spirit and scope of the disclosure.

In addition, all ranges disclosed herein are to be understood toencompass any and all subranges subsumed therein. For example, a statedrange of “1.0 to 10.0” should be considered to include any and allsubranges beginning with a minimum value of 1.0 or more and ending witha maximum value of 10.0 or less, e.g., 1.0 to 5.3, or 4.7 to 10.0, or3.6 to 7.9.

All ranges disclosed herein are also to be considered to include the endpoints of the range, unless expressly stated otherwise. For example, arange of “between 5 and 10,” “from 5 to 10,” or “5-10” should generallybe considered to include the end points 5 and 10.

Further, when the phrase “up to” is used in connection with an amount orquantity, it is to be understood that the amount is at least adetectable amount or quantity. For example, a material present in anamount “up to” a specified amount can be present from a detectableamount and up to and including the specified amount.

The terms “three-dimensional printing system,” “three-dimensionalprinter,” “printing,” and the like generally describe various solidfreeform fabrication techniques for making three-dimensional articles orobjects by stereolithography, selective deposition, jetting, fuseddeposition modeling, multi-jet modeling, and other additivemanufacturing techniques now known in the art or that may be known inthe future that use a build material or ink to fabricatethree-dimensional objects.

I. Inks for 3D Printing

In one aspect, inks for use with a 3D printer are described herein. Insome embodiments, an ink described herein comprises a cyclopolymerizablemonomer. Additionally, an ink described herein, in some cases, furthercomprises one or more of the following: an oligomeric curable material,an additional monomeric curable material, at least one photoinitiator,at least one colorant, and one or more additives selected from the groupconsisting of inhibitors and stabilizing agents.

Turning now to specific components of inks, inks described hereincomprises a cyclopolymerizable monomer. The cyclopolymerizable monomercomprises an acrylate moiety and an ethenyl or ethynyl moiety. In someembodiments, the ethenyl moiety can be a vinyl moiety, an allyl moiety,or a (meth)acrylate moiety, where the term “(meth)acrylate” includes anacrylate or methacrylate, or a mixture or combination thereof. Theethynyl moiety, in some embodiments, is an acetylene ethyne group or apropargyl group. Further, the α-carbon of the acrylate moiety and theα-carbon of the ethenyl or ethynyl moiety have a 1,5-, 1,6-, 1,7-, or1,8-relationship. Not intending to be bound by theory, it is believedthat such a monomer is capable of being cured or polymerized viacyclopoylmerization. For example, the acrylate moiety and the ethenyl orethynyl moiety of the monomer can be cyclopolymerized to form a 5, 6, 7,or 8-membered ring. Cyclopolymerization of an exemplarycyclopolymerizable monomer described herein is shown in FIG. 1. Withoutintending to be bound by theory, it is further believed that thiscyclopolymerization may be at least partially responsible for theimproved mechanical characteristics observed in articles 3D-printedusing inks described herein, particularly when compared to otheracrylate-containing inks. Moreover, again not intending to be bound bytheory, it is further believed that cyclopolymerizable monomersdescribed herein are also capable of being polymerized or cured viaacrylate polymerization, and that the existence of this secondpolymerization or curing pathway may further improve the properties ofarticle formed from an ink comprising a cyclopolymerizable monomerdescribed herein. This second polymerization or curing pathway is alsoshown in FIG. 1.

Regarding specific suitable cyclopolymerizable monomers, in someembodiments, the cyclopolymerizable monomer of an ink described hereinhas the structure of Formula (I):

where X can be O, S, NH, NR₅, or CR₅R₆; R₁ can be H or a hydrocarbongroup having 1-10 carbon atoms; R₂ can be a hydrocarbon group having 1-4carbon atoms; R₃ can be a hydrocarbon group having 1-4 carbon atoms; R₄can be HC═CH₂ or C≡CH; R₅ can be a hydrocarbon group having 1-4 carbonatoms; R₆ can be a hydrocarbon group having 1-4 carbon atoms; and thetotal number of carbon atoms of R₂ and R₃ cannot exceed 5. Anyhydrocarbon group in Formula (I) can be branched or linear, saturated orunsaturated, and the hydrocarbon group may contain or be a saturated orunsaturated, substituted or un-substituted hydrocarbon ring.

In specific embodiments R₁ is H or a hydrocarbon group having 1-10carbon atoms, 1-9 carbon atoms, 1-8 carbon atoms, 1-7 carbon atoms, 2-6carbon atoms, 2-5 carbon atoms, or 2-4 carbon atoms. In a preferredembodiment, R₁ is a hydrocarbon group having 3-6 carbon atoms. In someembodiments, R₁ may be or contain a saturated or unsaturated,substituted or un-substituted, 5 to 10 carbon atom ring. For example, R₁may be a substituted or unsubstituted phenyl ring.

In specific embodiments, R₂ and R₃ are each, individually, a hydrocarbongroup having 1-4 carbon atoms, 1-3 carbon atoms, or 1-2 carbon atoms. R₂and R₃ may be the same or different. In a preferred embodiment, R₂ andR₃ are each, individually, linear, saturated hydrocarbon groups having1-2 carbon atoms, and the total number of carbon atoms of R₂ and R₃ doesnot exceed 4.

In some specific embodiments, R₅ and R₆ are each, individually, H or ahydrocarbon group having 1-4 carbon atoms, 1-3 carbon atoms, or 1-2carbon atoms. R₅ and R₆ may be the same or different.

In still other specific embodiments, a cyclopolymerizable monomer asshown in Formula (I), can have the specific structure shown in Formula(II):

The above-described cyclopolymerizable monomer can be present in an inkdescribed herein in any amount not inconsistent with the objectives ofthe present disclosure. In some cases, the cyclopolymerizable monomer,in total, is present in the ink in an amount up to about 70 wt. %, up toabout 60 wt. %, up to about 50 wt. %, up to about 40 wt. %, up to about30 wt. %, up to about 20 wt. %, or up to about 10 wt. %, based on thetotal weight of the ink. In some instances, an ink described hereincomprises about 10-70 wt. % of the cyclopolymerizable monomer, based onthe total weight of the ink. In some embodiments, an ink comprises about10-60 wt. %, 10-50 wt. %, 10-40 wt. %, 10-30 wt. %, 10-20 wt. %, 20-70wt. %, 20-60 wt. %, 20-50 wt. %, 20-45 wt. %, 20-40 wt. %, 20-35 wt. %,or 20-30 wt. % of the cyclopolymerizable monomer, based on the totalweight of the ink.

Turning now to other specific components of inks described herein, inksdescribed herein may further comprise one or more oligomeric curablematerials and/or one or more additional monomeric curable materials(where the additional monomeric curable material is “additional”relative to the cyclopolymerizable monomer described above). A curablematerial, for reference purposes herein, comprises a chemical speciesthat includes one or more curable or polymerizable moieties. A“polymerizable moiety,” for reference purposes herein, comprises amoiety that can be polymerized or cured to provide a printed 3D articleor object. Such polymerizing or curing can be carried out in any mannernot inconsistent with the objectives of the present disclosure. In someembodiments, for example, polymerizing or curing comprises irradiating apolymerizable or curable material with electromagnetic radiation havingsufficient energy to initiate a polymerization or cross-linkingreaction. For instance, in some cases, ultraviolet (UV) radiation can beused. Thus, in some instances, a polymerizable moiety comprises aphoto-polymerizable or photo-curable moiety, such as a UV-polymerizablemoiety. In some embodiments, a curable material described herein isphoto-polymerizable or photo-curable at wavelengths ranging from about300 nm to about 400 nm or from about 320 nm to about 380 nm.Alternatively, in other instances, a curable material isphoto-polymerizable at visible wavelengths of the electromagneticspectrum.

Moreover, a polymerization reaction, in some cases, comprises a freeradical polymerization reaction, such as that between points ofunsaturation, including points of ethyleneic unsaturation. Otherpolymerization reactions may also be used. As understood by one ofordinary skill in the art, a polymerization reaction used to polymerizeor cure a curable material described herein can comprise a reaction of aplurality of “monomers” or chemical species having one or morefunctional groups or moieties that can react with one another to formone or more covalent bonds.

One non-limiting example of a polymerizable moiety of a curable materialdescribed herein is an ethyleneically unsaturated moiety, such as avinyl moiety, allyl moiety, or (meth)acrylate moiety, where the term“(meth)acrylate” includes acrylate or methacrylate or a mixture orcombination thereof.

“Oligomeric” species, which are contained in the oligomeric curablematerial described herein, are themselves polymers or oligomers and havea relatively high molecular weight or a relatively high viscosity. Thesespecies are also capable of undergoing additional polymerization, suchas through one or more points of unsaturation described herein. Apopulation of oligomeric species in the oligomeric curable materialdescribed herein can have varying molecular structures and/or formulasthroughout the population (such as may be exhibited, for example, by aspecified mass of a urethane acrylate having a non-unity molecularweight distribution, or by a specified mass of an ethoxylatedpolyethylene glycol having a distribution of ethylene glycol unitsand/or a distribution of ethoxy units within the population). The weightaverage molecular weight of an oligomeric curable material describedherein can generally be in the range from about 400 to 10,000, fromabout 600 to 10,000, or from about 500 to 7,000.

In contrast to an “oligomeric” species, “monomeric” species, which arecontained in the additional monomeric material described herein, are notthemselves a polymer or oligomer, and have a relatively low molecularweight or a relatively low viscosity. “Monomeric” species contained inthe additional monomeric curable material can have a consistent orwell-defined molecular structure and/or formula throughout thepopulation (such as may be exhibited, for instance, by a specified massof ethoxylated (4) bisphenol A diacrylate or a specific mass of theabove-described curable monomer). Additionally, in some embodiments, anadditional monomeric curable material as described herein has aviscosity of 500 centipoise (cP) or less at 25° C., when measuredaccording to ASTM D2983, while an “oligomeric” curable material has aviscosity of 1000 cP or more at 25° C., when measured according to ASTMD2983.

One non-limiting example of a polymerizable moiety of the oligomericcurable material or the additional monomeric curable material describedherein is an ethylenically unsaturated moiety, such as a vinyl moiety,allyl moiety, or (meth)acrylate moiety, where the term “(meth)acrylate”includes acrylate or methacrylate or a mixture or combination thereof.

Additionally, the oligomeric curable material and the additionalmonomeric curable material described herein can comprise amonofunctional, difunctional, trifunctional, tetrafunctional,pentafunctional, or higher functional curable species. A“monofunctional” curable species, for reference purposes herein,comprises a chemical species that includes one curable or polymerizablemoiety. Similarly, a “difunctional” curable species comprises a chemicalspecies that includes two curable or polymerizable moieties; a“trifunctional” curable species comprises a chemical species thatincludes three curable or polymerizable moieties; a “tetrafunctional”curable species comprises a chemical species that includes four curableor polymerizable moieties; and a “pentafunctional” curable speciescomprises a chemical species that includes five curable or polymerizablemoieties. Thus, in some embodiments, a monofunctional curable materialof an ink described herein comprises a mono(meth)acrylate, adifunctional curable material of an ink described herein comprises adi(meth)acrylate, a trifunctional curable material of an ink describedherein comprises a tri(meth)acrylate, a tetrafunctional curable materialof an ink described herein comprises a tetra(meth)acrylate, and apentafunctional curable material of an ink described herein comprises apenta(meth)acrylate. Other monofunctional, difunctional, trifunctional,tetrafunctional, and pentafunctional curable materials may also be used.

Moreover, a monofunctional, difunctional, trifunctional,tetrafunctional, and pentafunctional curable material, in some cases,can comprise a relatively low molecular weight species, i.e., amonomeric species, or a relatively high molecular weight species, i.e.,an oligomeric species.

In general, any oligomeric curable material not inconsistent with theobjectives of the present disclosure may be used in an ink describedherein. In some cases, for instance, an oligomeric curable materialcomprises a polyester (meth)acrylate oligomer, a urethane (meth)acrylateoligomer, or an epoxy(meth)acrylate oligomer. Further, in someembodiments, an oligomeric curable material described herein comprisesan aliphatic polyester urethane acrylate oligomer and/or an acrylateamine oligomeric resin, such as EBECRYL 7100. In some cases, anoligomeric curable material described herein comprises a polypropyleneglycol mono(meth)acrylate or polyethylene glycol mono(meth)acrylate. Insome embodiments, an oligomeric curable material comprises amonofunctional aliphatic urethane (meth)acrylate. Moreover, in somecases, an oligomeric curable material comprises a diacrylate and/ordimethacrylate ester of an aliphatic, cycloaliphatic or aromatic diol,including polyethylene glycol, ethoxylated or propoxylated neopentylglycol, ethoxylated or propoxylated bisphenol A, ethoxylated orpropoxylated bisphenol F, ethoxylated or propoxylated bisphenol S,ethoxylated or propoxylated 1,1,1-trimethylolpropanetri(meth)acrylate,or ethoxylated or propoxylated glycerol tri(meth)acrylate.

Moreover, an oligomeric curable material consistent with the objectivesof the present disclosure, in some instances, does not include a polymeror oligomer comprising or formed from one or more structural unitsderived from a cyclopolymerizable monomer as described herein, e.g., acyclopolymerizable monomer according to Formula (II). Similarly, in somecases, the oligomeric curable material does not include a polymer oroligomer comprising structural units derived from a cyclopolymerizablemonomer as described herein (e.g., a cyclopolymerizable monomeraccording to Formula (II)), and at least one monomer selected from thegroup consisting of (meth)acrylic ester, (meth)acrylamide, unsaturatedmonocarboxylic acid, and aromatic vinyl and N-substituted maleimide.Instead, in some preferred embodiments, inks described herein contain acyclopolymerizable monomer as described herein (e.g., acyclopolymerizable monomer according to Formula (II)), only as amonomeric curable material prior to curing.

Some non-limiting examples of commercially available oligomeric curablematerials useful in some embodiments described herein include thefollowing: alkoxylated tetrahydrofurfuryl acrylate, commerciallyavailable from SARTOMER under the trade name SR 611; monofunctionalurethane acrylate, commercially available from RAHN USA under the tradename GENOMER 1122; an aliphatic urethane diacrylate, commerciallyavailable from ALLNEX under the trade name EBECRYL 8402; amultifunctional acrylate oligomer, commercially available from DYMAXCorporation under the trade name BR-952; aliphatic polyether urethaneacrylate, commercially available from DYMAX Corporation under the tradename BR-371 S; and an aliphatic polyether urethane methacrylate,commercially available from DYMAX Corporation under the trade nameBR-541 MB. Other commercially available oligomeric curable materials mayalso be used.

Urethane (meth)acrylates suitable for use in inks described herein, insome cases, can be prepared in a known manner, typically by reacting ahydroxyl-terminated urethane with acrylic acid or methacrylic acid togive the corresponding urethane (meth)acrylate, or by reacting anisocyanate-terminated prepolymer with hydroxyalkyl acrylates ormethacrylates to give the urethane (meth)acrylate. Suitable processesare disclosed, inter alia, in EP-A 114 982 and EP-A 133 908. The weightaverage molecular weight of such (meth)acrylate oligomers, in somecases, can be from about 400 to 10,000 or from about 500 to 7,000.Urethane (meth)acrylates are also commercially available from SARTOMERunder the product names CN980, CN981, CN975 and CN2901, or from BOMARSpecialties Co. under the product name BR-741. In some embodimentsdescribed herein, a urethane (meth)acrylate oligomer has a viscosityranging from about 140,000 centipoise (cP) to about 160,000 cP at about50° C. or from about 125,000 cP to about 175,000 cP at about 50° C. whenmeasured in a manner consistent with ASTM D2983. In some cases, aurethane (meth)acrylate oligomer has a viscosity ranging from about100,000 cP to about 200,000 cP at about 50° C. or from about 10,000 cPto about 300,000 cP at about 50° C. when measured in a manner consistentwith ASTM D2983.

The oligomeric curable material can be present in an ink describedherein in any amount not inconsistent with the objectives of the presentdisclosure. In some cases, the oligomeric curable material, in total, ispresent in the ink in an amount up to about 80 wt. %, up to about 70 wt.%, up to about 60 wt. %, up to about 50 wt. %, up to about 40 wt. %, upto about 30 wt. %, or up to about 20 wt. %, based on the total weight ofthe ink. In some instances, an ink described herein comprises about10-80 wt. % of the oligomeric curable material, based on the totalweight of the ink. In some embodiments, an ink comprises about 10-70 wt.%, 10-60 wt. %, 10-50 wt. %, 10-40 wt. %, 10-30 wt. %, 10-20 wt. %,15-80 wt. %, 15-70 wt. %, 15-40 wt. %, 15-30 wt. %, 20-80 wt. %, 20-70wt. %, 20-60 wt. %, 20-50 wt. %, 20-40 wt. %, 30-80 wt. %, 30-70 wt. %,30-60 wt. %, 30-50 wt. %, 40-80 wt. %, 40-70 wt. %, or 40-60 wt. % ofthe oligomeric curable material, based on the total weight of the ink.

In addition, any monomeric curable materials not inconsistent with theobjectives of the present disclosure may be used as the additionalmonomeric curable material described herein. In some cases, theadditional monomeric curable material of an ink described hereincomprises one or more species of (meth)acrylates, such as one or moremonofunctional, difunctional, trifunctional, tetrafunctional(meth)acrylates, and/or pentafunctional (meth)acrylates. In someembodiments, for instance, a monomeric curable material comprises methyl(meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl(meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate,2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl(meth)acrylate, n-dodecyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate,2- or 3-hydroxypropyl (meth)acrylate, 2-methoxyethyl (meth)acrylate,2-ethoxyethyl (meth)acrylate, 2- or 3-ethoxypropyl (meth)acrylate,tetrahydrofurfuryl methacrylate, isobornyl (meth)acrylate,2-(2-ethoxyethoxy)ethyl acrylate, cyclohexyl methacrylate,2-phenoxyethyl acrylate, glycidyl acrylate, isodecyl acrylate,2-phenoxyethyl (meth)acrylate, lauryl methacrylate, or a combinationthereof. In some embodiments, a monomeric curable material comprises oneor more of allyl acrylate, allyl methacrylate, triethylene glycoldi(meth)acrylate, tricyclodecane dimethanol diacrylate, and cyclohexanedimethanol diacrylate. Additionally, in some cases, a monomeric curablematerial comprises diacrylate and/or dimethacrylate esters of aliphatic,cycloaliphatic or aromatic diols, including 1,3- or 1,4-butanediol,neopentyl glycol, 1,6-hexanediol, diethylene glycol, triethylene glycol,tetraethylene glycol, tripropylene glycol,1,4-dihydroxymethylcyclohexane, 2,2-bis(4-hydroxycyclohexyl)propane orbis(4-hydroxycyclohexyl)methane, hydroquinone, 4,4′-dihydroxybiphenyl,bisphenol A, bisphenol F, or bisphenol S. A monomeric curable materialdescribed herein may also comprise 1,1-trimethylolpropanetri(meth)acrylate, pentaerythritol monohydroxy tri(meth)acrylate,dipentaerythritol monohydroxy penta(meth)acrylate, and/orbis(trimethylolpropane) tetra(meth)acrylate. Further, in some cases, amonomeric curable material can comprise an ethoxylated or propoxylatedspecies, such as ethoxylated or propoxylated neopentyl glycol,ethoxylated or propoxylated bisphenol A, ethoxylated or propoxylatedbisphenol F, ethoxylated or propoxylated bisphenol S, ethoxylated orpropoxylated 1,1,1-trimethylolpropanetri(meth)acrylate, or ethoxylatedor propoxylated glycerol tri(meth)acrylate.

Additional non-limiting examples of commercially available monomericcurable materials useful as the additional monomeric curable material insome embodiments described herein include the following: isobornylacrylate (IBOA), commercially available from SARTOMER under the tradename SR 506; isobornyl methacrylate, commercially available fromSARTOMER under the trade name SR 423A; triethylene glycol diacrylate,commercially available from SARTOMER under the trade name SR 272;triethylene glycol dimethacrylate, commercially available from SARTOMERunder the trade name SR 205; tricyclodecane dimethanol diacrylate,commercially available from SARTOMER under the trade name SR 833S;tris(2-hydroxy ethyl)isocyanurate triacrylate, commercially availablefrom SARTOMER under the trade name SR 368; 2-phenoxyethyl acrylate,commercially available from SARTOMER under the trade name SR 339;ethyoxylated (3 mole) bisphenol A diacrylate, commercially availablefrom SARTOMER under the trade name SR 349; a cyclic monofunctionalacrylate, commercially available by RAHN USA Corp. under the trade nameGENOMER 1120; and dipentaerythritol pentaacrylate, commerciallyavailable from SARTOMER under the trade name SR 399 LV. Othercommercially available monomeric curable materials may also be used.

The additional monomeric curable material can be present in an inkdescribed herein in any amount not inconsistent with the objectives ofthe present disclosure. In some cases, the monomeric curable material,in total, is present in an amount up to about 80 wt. %, up to about 70wt. %, up to about 60 wt. %, or up to about 50 wt. %, based on the totalweight of the ink. In some cases, an ink described herein comprisesabout 0-80 wt. % additional monomeric curable material, based on thetotal weight of the ink. In some embodiments, an ink comprises about0-75 wt. %, 0-70 wt. %, 0-60 wt. %, 0-50 wt. %, 0-40 wt. %, 0-35 wt. %,0-30 wt. %, 0-25 wt. %, 0-20 wt. %, 0-15 wt. %, 0-10 wt. %, or 0-5 wt. %additional monomeric curable material, based on the total weight of theink.

Turning to another component of inks described herein, inks describedherein can further comprise at least one photoinitiator. Anyphotoinitiator not inconsistent with the objectives of the presentdisclosure may be used. In some cases, a photoinitiator comprises analpha-cleavage type (unimolecular decomposition process) photoinitiatoror a hydrogen abstraction photosensitizer-tertiary amine synergist,operable to absorb light between about 250 nm and about 400 nm orbetween about 300 nm and about 385 nm, to yield free radical(s).Examples of alpha cleavage photoinitiators are Irgacure 184 (CAS947-19-3), Irgacure 369 (CAS 119313-12-1), and Irgacure 819 (CAS162881-26-7). An example of a photosensitizer-amine combination isDarocur BP (CAS 119-61-9) with diethylaminoethylmethacrylate.

In addition, in some instances, photoinitiators comprise benzoins,including benzoin, benzoin ethers, such as benzoin methyl ether, benzoinethyl ether and benzoin isopropyl ether, benzoin phenyl ether andbenzoin acetate, acetophenones, including acetophenone,2,2-dimethoxyacetophenone and 1,1-dichloroacetophenone, benzil, benzilketals, such as benzil dimethyl ketal and benzil diethyl ketal,anthraquinones, including 2-methylanthraquinone, 2-ethylanthraquinone,2-tert-butylanthraquinone, 1-chloroanthraquinone and2-amylanthraquinone, triphenylphosphine, benzoylphosphine oxides, suchas 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin TPO),benzophenones, such as benzophenone and4,4′-bis(N,N′-dimethylamino)benzophenone, thioxanthones and xanthones,acridine derivatives, phenazine derivatives, quinoxaline derivatives or1-phenyl-1,2-propanedione, 2-O-benzoyl oxime, 1-aminophenyl ketones or1-hydroxyphenyl ketones, such as 1-hydroxycyclohexyl phenyl ketone,phenyl 1-hydroxyisopropyl ketone and 4-isopropylphenyl1-hydroxyisopropyl ketone.

Photoinitiators can also comprise photoinitiators operable for use witha HeCd laser radiation source, including acetophenones,2,2-dialkoxybenzophenones and 1-hydroxyphenyl ketones, such as1-hydroxycyclohexyl phenyl ketone or 2-hydroxyisopropyl phenyl ketone(=2-hydroxy-2,2-dimethylacetophenone). Additionally, in some cases,photoinitiators comprise photoinitiators operable for use with an Arlaser radiation source including benzil ketals, such as benzil dimethylketal. In some embodiments, a suitable photoinitiator comprises anα-hydroxyphenyl ketone, benzil dimethyl ketal or2,4,6-trimethylbenzoyldiphenylphosphine oxide or a mixture thereof.

Another class of photoinitiators that may be included in an inkdescribed herein comprises ionic dye-counter ion compounds capable ofabsorbing actinic radiation and generating free radicals forpolymerization initiation. Some ionic dye-counter ion compounds andtheir mode of operation are disclosed in EP-A-0 223 587 and U.S. Pat.Nos. 4,751,102; 4,772,530; and 4,772,541.

A photoinitiator can be present in an ink described herein in any amountnot inconsistent with the objectives of the present disclosure. In someembodiments, a photoinitiator is present in an ink in an amount of up toabout 5 wt. %, based on the total weight of the ink. In some cases, aphotoinitiator is present in an amount ranging from about 0.1 wt. % toabout 5 wt. %.

Additionally, in some embodiments, an ink described herein furthercomprises one or more photosensitizers. In general, such a sensitizercan be added to an ink to increase the effectiveness of one or morephotoinitiators that may also be present. In some cases, a sensitizercomprises isopropylthioxanthone (ITX) or 2-chlorothioxanthone (CTX).

A sensitizer can be present in an ink in any amount not inconsistentwith the objectives of the present disclosure. In some embodiments, asensitizer is present in an amount ranging from about 0.1 wt. % to about2 wt. % or from about 0.5 wt. % to about 1 wt. %, based on the totalweight of the ink.

Turning to another component of the ink described herein, inks describedherein can also comprise at least one colorant. The colorant of an inkdescribed herein can be a particulate colorant, such as a particulatepigment, or a molecular colorant, such as a molecular dye. Any suchparticulate or molecular colorant not inconsistent with the objectivesof the present disclosure may be used. In some cases, for instance, thecolorant of an ink comprises an inorganic pigment, such as TiO₂ and/orZnO. In some embodiments, the colorant of an ink comprises a colorantfor use in a RGB, sRGB, CMY, CMYK, L*a*b*, or Pantone® colorizationscheme. In some instances, one or more colorants of an ink describedherein exhibits a white color. In other cases, a colorant exhibits ablack color. Some non-limiting examples of colorants suitable for use insome embodiments described herein include SUN UVDJ107, SUN UVDJ150, SUNUVDj322, SUN UVDj350, SUN UVDJ354, RjA D3010-FX-Y150, RjA D3410-FX-Y150,RjA D3410-FX-K, PENN COLOR 9B898, PENN COLOR 9B989, DNS-GKC-103W, and ObWhite Dye. Moreover, in some cases, a particulate colorant describedherein has an average particle size of less than about 5 μm, or lessthan about 1 μm. In some instances, a particulate colorant describedherein has an average particle size of less than about 500 nm, such asan average particle size of less than about 400 nm, less than about 300nm, less than about 250 nm, less than about 200 nm, or less than about150 nm. In some instances, a particulate colorant has an averageparticle size of about 50-5000 nm, about 50-1000 nm, or about 50-500 nm.

A colorant can be present in an ink described herein in any amount notinconsistent with the objectives of the present disclosure. In somecases, colorant is present in the ink in an amount up to about 2 wt. %,or an amount of about 0.005-2 wt. %, 0.01-2 wt. %, 0.01-1.5 wt. %,0.01-1 wt. %, 0.01-0.5 wt. %, 0.1-2 wt. %, 0.1-1 wt. %, 0.1-0.5 wt. %,or 0.5-1.5 wt. %, based on the total weight of the ink.

Moreover, inks described herein, in some embodiments, further compriseone or more other additives. In some cases, for example, an inkdescribed herein further comprises one or more polymerization inhibitorsand/or stabilizing agents. A polymerization inhibitor can be added to anink to provide additional thermal stability to the composition. Anypolymerization inhibitor not inconsistent with the objectives of thepresent disclosure may be used. Moreover, a polymerization inhibitor canretard or decrease the rate of polymerization, and/or preventpolymerization from occurring for some period of time or “inductiontime” until the polymerization inhibitor is consumed. Further, in somecases, a polymerization inhibitor described herein is an “addition type”inhibitor. An inhibitor described herein can also be a “chain transfertype” inhibitor. In some instances, a suitable polymerization inhibitorcomprises methoxyhydroquinone (MEHQ).

A stabilizing agent, in some embodiments, comprises one or moreanti-oxidants. A stabilizing agent can comprise any anti-oxidant notinconsistent with the objectives of the present disclosure. In somecases, suitable anti-oxidants include various aryl compounds, includingbutylated hydroxytoluene (BHT), which can also be used as apolymerization inhibitor in some embodiments described herein. Moregenerally, a single species may serve as both a stabilizing agent and apolymerization inhibitor. It is also possible, in some cases, to use aplurality of inhibitors and/or stabilizing agents, wherein differinginhibitors and/or stabilizers provide differing effects and/or worksynergistically.

A polymerization inhibitor and/or a stabilizing agent can be present inan ink in any amount not inconsistent with the objectives of the presentdisclosure. In some embodiments, a polymerization inhibitor is presentin an amount ranging from about 0.01 wt. % to about 2 wt. % or fromabout 0.05 wt. % to about 1 wt. %. Similarly, in some cases, astabilizing agent is present in an ink in an amount ranging from about0.1 wt. % to about 5 wt. %, from about 0.5 wt. % to about 4 wt. %, orfrom about 1 wt. % to about 3 wt. %, based on the total weight of theink.

In some embodiments, an ink described herein may contain viscositymodifying agents. Non-limiting examples of viscosity modifying agentsinclude a saturated fatty acid or a combination of saturated fattyacids, or an oil, such as a plant oil. The inks described herein maycomprise up to 5 wt. % up to 3 wt. %, up to 1 wt. %, up to 0.5 wt. %, orup to 0.1 wt. % of a viscosity modifying agent not inconsistent with theobject of this invention.

Similarly, in some cases, an ink described herein can include anon-curable polymer or oligomer. Such a “non-curable” polymer oroligomer can exclude or be free from a polymerizable moiety describedhereinabove, such as an ethyleneically unsaturated moiety or otherphotocurable moiety. Of course, it is to be understood that such a“non-curable” polymer or oligomer does not include a polymerizablemoiety in the polymer or oligomer backbone (and/or in a pendant group ofthe polymer or oligomer) after formation of the non-curable polymer oroligomer (as opposed to not including a polymerizable moiety prior toformation of the non-curable polymer or oligomer). Non-limiting examplesof non-curable polymers or oligomers described herein includepolyolefins such as polyethylene or polypropylene, polydienes,polyamides, polyesters, and polyacrylonitriles. Additionally, in someinstances, a non-curable polymer or oligomer comprises a copolymer, suchas a polyolefin copolymer (e.g., a polypropylene copolymer, or PPC) or apolydiene-polyacrylonitrile copolymer (e.g., a butadiene-acrylonitrilecopolymer).

Inks described herein can exhibit a variety of desirable properties. Forexample, an ink described herein can have any freezing point, meltingpoint, and/or other phase transition temperature not inconsistent withthe objectives of the present disclosure. In some cases, an ink hasfreezing and melting points consistent with temperatures used in some 3Dprinting systems, including 3D printing systems designed for use withphase changing inks. In some embodiments, the freezing point of an inkis greater than about 40° C. In some instances, for example, an ink hasa freezing point centered at a temperature ranging from about 45° C. toabout 55° C. or from about 50° C. to about 80° C. In some cases, an inkhas a freezing point below about 40° C. or below about 30° C.

Further, in some embodiments described herein, an ink exhibits a sharpfreezing point or other phase transition. In some cases, for instance,an ink freezes over a narrow range of temperatures, such as a range ofabout 1-10° C., about 1-8° C., or about 1-5° C. In some embodiments, anink having a sharp freezing point freezes over a temperature range ofX±2.5° C., where X is the temperature at which the freezing point iscentered (e.g., X=65° C.).

In addition, an ink described herein, in some cases, is fluid at jettingtemperatures encountered in some 3D printing systems. Moreover, in someembodiments, an ink solidifies once deposited on a surface during thefabrication of a three-dimensionally printed article or object.Alternatively, in other instances, an ink remains substantially fluidupon deposition on a surface. Solidification of an ink, in someembodiments, occurs through a phase change of the ink or a component ofthe ink. The phase change can comprise a liquid to solid phase change ora liquid to semi-solid phase change. Further, in some instances,solidification of an ink comprises an increase in viscosity of the ink,such as an increase in viscosity from a low viscosity state to a highviscosity state. Solidification of an ink can also occur due to curingof the ink.

Additionally, in some embodiments, the inks described herein, whennon-cured, has a viscosity profile consistent with the requirements andparameters of one or more 3D printing systems, such as an MiP or SLAsystem. For example, in some cases, an ink described herein has adynamic viscosity at 30° C. of 1600 centipoise (cP) or less, 1200 cP orless, or 800 cP or less. In a preferred embodiment, an ink describedherein has a dynamic viscosity of 500 cP or less at 30° C., whenmeasured according to ASTM standard D2983 (e.g., using a BrookfieldModel DV-II+ Viscometer). In some cases, an ink described herein whennon-cured exhibits a dynamic viscosity of about 200-1600 cP, about200-1200 cP, about 200-800 cP, about 200-500 cP, or about 200-400 cP at30° C., when measured according to ASTM D2983.

Inks described herein can also exhibit a variety of desirableproperties, in addition to those described hereinabove, in a curedstate. An ink in a “cured” state, as used herein, comprises an ink thatincludes a curable material or polymerizable component that has been atleast partially cured, i.e., at least partially polymerized and/orcross-linked. For instance, in some cases, a cured ink is at least about70% polymerized or cross-linked or at least about 80% polymerized orcross-linked. In some embodiments, a cured ink is at least about 85%, atleast about 90%, at least about 95%, at least about 98%, or at least 99%polymerized or cross-linked. In some instances, a cured ink is betweenabout 80% and about 99% polymerized or cross-linked.

In some cases, an ink described herein, when cured, has an elongation atbreak of about 10 to 70%, about 10 to 60%, about 15 to 50%, or about 20to 50%, when measured according to ASTM D638. Further, a cured inkdescribed herein, in some cases, can have a tensile strength of about 40to 70 MPa about 40 to 60 MPa, or about 45 to 55 MPa when measuredaccording to ASTM D638. Additionally, a cured ink described herein, insome embodiments, can have a tensile modulus of about 1800 to 2100 MPa,about 1900 to 2100 MPa, or about 1950 to 2050 MPa when measuredaccording to ASTM D638. Also, a cured ink described herein can have animpact resistance of 1 to 4 ft·lb/in (Notched), 1 to 3 ft·lb/in(Notched), or 1 to 2 ft·lb/in (Notched) when measured according to ASTMD256. Finally, in some cases, a cured ink described herein has a flexualmodulus of 2000 to 2500 MPa, 2100 to 2400 MPa, or 2100 to 2200 MPa whenmeasured according to ASTM D790.

Moreover, in some cases, an ink described herein, when cured, canexhibit a plurality of the foregoing properties. For example, in someembodiments, an ink when cured has a tensile strength of about 40-70 MPawhen measured according to ASTM D638; an impact resistance of 1 to 4ft·lb/in (Notched), when measured according to ASTM D256; and anelongation at break of about 10-70% when measured according to ASTMD638.

Inks described herein can be produced in any manner not inconsistentwith the objectives of the present disclosure. In some embodiments, forinstance, a method for the preparation of an ink described hereincomprises the steps of mixing the components of the ink, melting themixture, and filtering the molten mixture. Melting the mixture, in somecases, is carried out at a temperature of about 75° C. or in a rangefrom about 75° C. to about 85° C. In some embodiments, an ink describedherein is produced by placing all components of the ink in a reactionvessel and heating the resulting mixture to a temperature ranging fromabout 75° C. to about 85° C. with stirring. The heating and stirring arecontinued until the mixture attains a substantially homogenized moltenstate. In general, the molten mixture can be filtered while in aflowable state to remove any large undesirable particles that mayinterfere with jetting or extrusion or other printing process. Thefiltered mixture can then be cooled to ambient temperatures and storeduntil ready for use in a 3D printing system.

II. Methods of Printing a 3D Article

In another aspect, methods of printing a 3D article or object aredescribed herein. Methods of printing a 3D article or object describedherein can include forming the 3D article from a plurality of layers ofan ink described herein in a layer-by-layer manner. Any ink describedhereinabove in Section I may be used. For example, in some cases, theink comprises 10-70 or 20-40 wt. % of a cyclopolymerizable monomerdescribed in Section I above, based on the total weight of the ink.Additionally, in some embodiments, the ink has a dynamic viscosity of1,600 cP or less or 500 cP or less at 30° C. Further, the layers of anink can be deposited according to an image of the 3D article in acomputer readable format. In some embodiments, the ink is depositedaccording to preselected computer aided design (CAD) parameters.Moreover, in some cases, one or more layers of an ink described hereinhas a thickness of about 10 μm to about 100 μm, about 10 μm to about 80μm, about 10 μm to about 50 μm, about 20 μm to about 100 μm, about 20 μmto about 80 μm, or about 20 μm to about 40 μm. Other thicknesses arealso possible.

Additionally, it is to be understood that methods of printing a 3Darticle described herein can include, for example, MjP or SLA 3Dprinting methods. For example, in some instances, a MjP method ofprinting a 3D article comprises selectively depositing layers of an inkdescribed herein in a fluid state onto a substrate, such as a build padof a 3D printing system. In addition, in some embodiments, a methoddescribed herein further comprises supporting at least one of the layersof the ink with a support material. Any support material notinconsistent with the objectives of the present disclosure may be used.

A method described herein can also comprise curing the layers of theink. For example, in some instances, a method of printing a 3D articledescribed herein further comprises subjecting the ink to electromagneticradiation of sufficient wavelength and intensity to cure the ink, wherecuring can comprise polymerizing one or more polymerizable moieties orfunctional groups of one or more components of the ink. In some cases, alayer of deposited ink is cured prior to the deposition of another oradjacent layer of ink. Additionally, curing one or more layers ofdeposited ink, in some embodiments, is carried out by exposing the oneor more layers to electromagnetic radiation, such as UV light, visiblelight, or infrared light.

Further details regarding various methods, including “materialdeposition” methods (such as MjP) or “vat polymerization” methods (suchas SLA), are provided below.

A. Material Deposition Methods

In a material deposition method, one or more layers of an ink describedherein are selectively deposited onto a substrate and cured. Curing ofthe ink may occur after selective deposition of one layer, each layer,several layers, or all layers of the ink.

In some instances, an ink described herein is selectively deposited in afluid state onto a substrate, such as a build pad of a 3D printingsystem. Selective deposition may include, for example, depositing theink according to preselected CAD parameters. For example, in someembodiments, a CAD file drawing corresponding to a desired 3D article tobe printed is generated and sliced into a sufficient number ofhorizontal slices. Then, the ink is selectively deposited, layer bylayer, according to the horizontal slices of the CAD file drawing toprint the desired 3D article. A “sufficient” number of horizontal slicesis the number necessary for successful printing of the desired 3Darticle, e.g., to produce it accurately and precisely.

Further, in some embodiments, a preselected amount of ink describedherein is heated to the appropriate temperature and jetted through aprint head or a plurality of print heads of a suitable inkjet printer toform a layer on a print pad in a print chamber. In some cases, eachlayer of ink is deposited according to preselected CAD parameters. Asuitable print head to deposit the ink, in some embodiments, is apiezoelectric print head. Additional suitable print heads for thedeposition of ink and support material described herein are commerciallyavailable from a variety of ink jet printing apparatus manufacturers.For example, Xerox, Hewlett Packard, or Ricoh print heads may be used insome instances.

Additionally, in some embodiments, an ink described herein remainssubstantially fluid upon deposition. Alternatively, in other instances,the ink exhibits a phase change upon deposition and/or solidifies upondeposition. Moreover, in some cases, the temperature of the printingenvironment can be controlled so that the jetted droplets of inksolidify on contact with the receiving surface. In other embodiments,the jetted droplets of ink do not solidify on contact with the receivingsurface, remaining in a substantially fluid state. Additionally, in someinstances, after each layer is deposited, the deposited material isplanarized and cured with electromagnetic (e.g., UV, visible or infraredlight) radiation prior to the deposition of the next layer. Optionally,several layers can be deposited before planarization and curing, ormultiple layers can be deposited and cured followed by one or morelayers being deposited and then planarized without curing. Planarizationcorrects the thickness of one or more layers prior to curing thematerial by evening the dispensed material to remove excess material andcreate a uniformly smooth exposed or flat up-facing surface on thesupport platform of the printer. In some embodiments, planarization isaccomplished with a wiper device, such as a roller, which may becounter-rotating in one or more printing directions but notcounter-rotating in one or more other printing directions. In somecases, the wiper device comprises a roller and a wiper that removesexcess material from the roller. Further, in some instances, the wiperdevice is heated. It should be noted that the consistency of the jettedink described herein prior to curing, in some embodiments, shoulddesirably be sufficient to retain its shape and not be subject toexcessive viscous drag from the planarizer.

Moreover, a support material, when used, can be deposited in a mannerconsistent with that described hereinabove for the ink. The supportmaterial, for example, can be deposited according to the preselected CADparameters such that the support material is adjacent or continuous withone or more layers of the ink. Jetted droplets of the support material,in some embodiments, solidify or freeze on contact with the receivingsurface. In some cases, the deposited support material is also subjectedto planarization, curing, or planarization and curing. Any supportmaterial not inconsistent with the objectives of the present disclosuremay be used.

Layered deposition of the ink and support material can be repeated untilthe 3D article has been formed. In some embodiments, a method ofprinting a 3D article further comprises removing the support materialfrom the ink.

Curing of the ink may occur after selective deposition of one layer ofink, of each layer of ink, of several layers of ink, or of all layers ofthe ink necessary to print the desired 3D article. In some embodiments,a partial curing of the deposited ink is performed after selectivedeposition of one layer of ink, each layer of ink, several layers ofink, or all layers of the ink necessary to print the desired 3D article.A “partially cured” ink, for reference purposes herein, is one that canundergo further curing. For example, a partially cured ink is up toabout 30% polymerized or cross-linked or up to about 50% polymerized orcross-linked. In some embodiments, a partially cured ink is up to about60%, up to about 70%, up to about 80%, up to about 90%, or up to about95% polymerized or cross-linked.

In some embodiments, partial curing of the deposited ink can includeirradiating the ink with an electromagnetic radiation source orphotocuring the ink. Any electromagnetic radiation source notinconsistent with the objectives of the present disclosure may be used,e.g., an electromagnetic radiation source that emits UV, visible orinfrared light. For example, in some embodiments, the electromagneticradiation source can be one that emits light having a wavelength fromabout 300 nm to about 900 nm, e.g., a Xe arc lamp.

Moreover, in some embodiments, partial curing of an ink described hereinincludes polymerizing the acrylate moiety of the cyclopolymerizablemonomer and/or polymerizing one or more other (meth)acrylate-containingspecies of the ink via (meth)acrylate polymerization. In some cases,partial curing primarily includes such (meth)acrylate polymerization.For example, in some instances, more than 50%, more than 60%, or morethan 70% of the polymerization occurs via acrylate polymerization,rather than via some other polymerization route, e.g.,cyclopolymerization of the acrylate moiety and the ethenyl or ethynylmoiety of the ink. During partial curing, which is performed during thebuild of a desired 3D article, some or none of the polymerization mayoccur via a route other than a (meth)acrylate polymerization route.

Further, in some embodiments, a post-curing is performed after partiallycuring is performed. For example, in some cases, post-curing is carriedout after selectively depositing all layers of the ink necessary to forma desired 3D article, after partially curing all layers of the ink, orafter both of the foregoing steps have been performed. Moreover, in someembodiments, post-curing comprises photocuring. Any electromagneticradiation source not inconsistent with the objectives of the presentdisclosure may be used for a post-curing step described herein. Forexample, in some embodiments, the electromagnetic radiation source canbe a light source that has a higher energy, a lower energy, or the sameenergy as the electromagnetic radiation source used for partial curing.In some cases wherein the electromagnetic radiation source used forpost-curing has a higher energy (i.e., a shorter wavelength) than thatused for partial curing, an Xe arc lamp can be used for partial curingand a Hg lamp can be used for post-curing.

Additionally, in some instances, post-curing of deposited layers of anink described herein includes cyclopolymerizing the acrylate moiety andthe ethenyl or ethynyl moiety of the cyclopolymerizable monomer of theink. In some cases, post-curing primarily includes suchcyclopolymerization. For example, in some embodiments, more than 50%,more than 60%, or more than 70% of the polymerization, duringpost-curing, occurs via cyclopolymerization rather than by some otherroute, e.g., via (meth)acrylate polymerization. During post-curing, someor none of the polymerization may occur via a route other thancyclopolymerization described herein.

Additionally, after post-curing, in some cases, the deposited layers ofink are at least about 80% polymerized or cross-linked or at least about85% polymerized or cross-linked. In some embodiments, the depositedlayers of ink are at least about 90%, at least about 95%, at least about98%, or at least about 99% polymerized or cross-linked. In someinstances, the deposited layers of ink are bout 80-100%, about 80-99%,about 80-95%, about 85-100%, about 85-99%, about 85-95%, about 90-100%,or about 90-99% polymerized or cross-linked.

B. Vat Polymerization Methods

It is also possible to form a 3D article from an ink described hereinusing a vat polymerization method, such as an SLA method. Thus, in somecases, a method of printing a 3D article described herein comprisesretaining an ink described herein in a fluid state in a container andselectively applying energy to the ink in the container to solidify atleast a portion of a fluid layer of the ink, thereby forming asolidified layer that defines a cross-section of the 3D article.Additionally, a method described herein can further comprise raising orlowering the solidified layer of ink to provide a new or second fluidlayer of unsolidified ink at the surface of the fluid ink in thecontainer, followed by again selectively applying energy to the ink inthe container to solidify at least a portion of the new or second fluidlayer of the ink to form a second solidified layer that defines a secondcross-section of the 3D article. Further, the first and secondcross-sections of the 3D article can be bonded or adhered to one anotherin the z-direction (or build direction corresponding to the direction ofraising or lowering recited above) by the application of the energy forsolidifying the ink. Moreover, selectively applying energy to the ink inthe container can comprise applying electromagnetic radiation having asufficient energy to cure the ink. In some instances, theelectromagnetic radiation has an average wavelength of 300-900 nm, andin other embodiments the electromagnetic radiation has an averagewavelength that is less than 300 nm. In some cases, the curing radiationis provided by a computer controlled laser beam. In addition, in somecases, raising or lowering a solidified layer of ink is carried outusing an elevator platform disposed in the container of fluid ink. Amethod described herein can also comprise planarizing a new layer offluid ink provided by raising or lowering an elevator platform. Suchplanarization can be carried out, in some cases, by a wiper or roller.

It is further to be understood that the foregoing process can berepeated a desired number of times to provide the 3D article. Forexample, in some cases, this process can be repeated “n” number oftimes, wherein n can be up to about 100,000, up to about 50,000, up toabout 10,000, up to about 5000, up to about 1000, or up to about 500.Thus, in some embodiments, a method of printing a 3D article describedherein can comprise selectively applying energy to an ink in a containerto solidify at least a portion of an nth fluid layer of the ink, therebyforming an nth solidified layer that defines an nth cross-section of the3D article, raising or lowering the nth solidified layer of ink toprovide an (n+1)th layer of unsolidified ink at the surface of the fluidink in the container, selectively applying energy to the (n+1)th layerof ink in the container to solidify at least a portion of the (n+1)thlayer of the ink to form an (n+1)th solidified layer that defines an(n+1)th cross-section of the 3D article, raising or lowering the (n+1)thsolidified layer of ink to provide an (n+2)th layer of unsolidified inkat the surface of the fluid ink in the container, and continuing torepeat the foregoing steps to form the 3D article. Further, it is to beunderstood that one or more steps of a method described herein, such asa step of selectively applying energy to a layer of ink, can be carriedout according to an image of the 3D article in a computer-readableformat. General methods of 3D printing using stereolithography arefurther described, inter alia, in U.S. Pat. Nos. 5,904,889 and6,558,606.

Performing a printing process described above can provide a printed 3Darticle from an ink described herein that has a high feature resolution.The “feature resolution” of an article, for reference purposes herein,can be the smallest controllable physical feature size of the article.The feature resolution of an article can be described in terms of a unitof distance such as microns (μm), or in terms of dots per inch (dpi). Asunderstood by one of ordinary skill in the art, a higher featureresolution corresponds to a higher dpi value but a lower distance valuein μm. In some cases, an article formed by depositing or solidifying anink described herein can have a feature resolution of about 500 μm orless, about 200 μm or less, about 100 μm or less, or about 50 μm orless, including at elevated temperatures. In some embodiments, anarticle has a feature resolution between about 50 μm and about 500 μm,between about 50 μm and about 200 μm, between about 50 μm and about 100μm, or between about 100 μm and about 200 μm. Correspondingly, in someinstances, an article described herein has a feature resolution of atleast about 100 dpi, at least about 200 dpi, at least about 250 dpi, atleast about 400 dpi, or at least about 500 dpi. In some cases, thefeature resolution of an article is between about 100 dpi and about 600dpi, between about 100 dpi and about 250 dpi, or between about 200 dpiand about 600 dpi.

In a vat polymerization method such as described above, the ink may bepartially cured as described in Section IIA above. For example, in someembodiments, selectively applying energy to the ink in the container tosolidify at least a portion of a fluid layer of the ink may includepartially curing at least a portion of a fluid layer of the ink. Inother embodiments, partial curing of at least a portion of a fluid layerof the ink may occur after a first layer of the ink is provided andsolidified, before or after a second layer of the ink is provided orsolidified, or before or after one, several, or all subsequent layers ofthe ink are provided or solidified.

Additionally, in some embodiments of a vat polymerization methoddescribed herein, after partial curing or after the desired 3D articleis formed, post-curing as described in Section IIA above may beperformed. The desired 3D article may be, for example, an article thatcorresponds to the design in a CAD file.

III. Printed 3D Articles

In another aspect, printed 3D articles are described herein. In someembodiments, a printed 3D article is formed from an ink describedherein. Any ink described hereinabove in Section I may be used. Forexample, in some cases, the ink comprises 10-70 or 20-40 wt. % of acyclopolymerizable monomer as described in Section I above, based on thetotal weight of the ink. Further, in some embodiments, the ink has adynamic viscosity, prior to curing, of 1,600 cP or less or 500 cP orless at 30° C. Moreover, in some cases, a printed 3D article describedherein, when cured (e.g., when post-cured), can exhibit mechanicalproperties similar to injection-molded thermoplastic articles. Forexample, such a printed 3D article can exhibit, in some cases, anelongation at break of about 10 to 70%, about 10 to 60%, about 15 to50%, or about 20 to 50%, when measured according to ASTM D638. Further,a printed 3D article described herein, in some cases, can have a tensilestrength of about 40 to 70 MPa about 40 to 60 MPa, or about 45 to 55 MPawhen measured according to ASTM D638. Additionally, a printed 3D articledescribed herein, in some embodiments, can have a tensile modulus ofabout 1800 to 2100 MPa, about 1900 to 2100 MPa, or about 1950 to 2050MPa when measured according to ASTM D638. Notably, a printed 3D articledescribed herein may have an impact resistance (Notched) of 1 to 4ft·lb/in (Notched), 1 to 3 ft·lb/in (Notched), or 1 to 2 ft·lb/in(Notched) when measured according to ASTM D256. Finally, a printed 3Darticle described herein may have a flexual modulus of 2000 to 2500 MPa,2100 to 2400 MPa, or 2100 to 2200 MPa when measured according to ASTMD790.

Some embodiments described herein are further illustrated in thefollowing non-limiting examples.

Examples

Inks according to some embodiments described herein were prepared asfollows. Specifically, to prepare various inks, the components of TableI were mixed in a reaction vessel. The amounts in Table I refer to thewt. % of each component of the identified ink, based on the total weightof the ink. For each ink, the appropriate mixture was heated to atemperature of about 75-85° C. with stirring. The heating and stirringwere continued until the mixture attained a substantially homogenizedmolten state. The molten mixture was then filtered. Next, the filteredmixture was allowed to cool to ambient temperature. The viscosity at 30°C. of Ink 1 and Comparative Ink 1 was measured according to ASTM D2983,and the results are included in Table II below.

TABLE I Ink Compositions. Comparative Comparative Ink 1 Ink 2 Ink 3 Ink4 Ink 1 Ink 2 Monomeric Curable 37.63 34.40 26.72 25.82 37.63 33.57Material Oligomeric Curable 56.47 61.92 63.71 65.41 56.47 63.01 MaterialPhotoinitiator 2.21 3.58 3.51 3.50 2.21 3.19 Colorant 0.08 0.10 0.040.04 0.08 0.23 Non-Curable 3.61 6.02 5.23 3.61 Polymer/Oligomer

In Table I above, the monomeric curable material for Inks 1, 2, 3, and 4was a cyclopolymerizable monomer having the structure of Formula (II)above. The monomeric curable material for Comparative Ink 1 was amixture of SR 339 and IBOA (15.59 and 22.04 wt. %, respectively). Themonomeric curable material for Comparative Ink 2 was a mixture of SR 339(25.24 wt. %) and Genomer 1120 (8.33 wt. %). The oligomeric curablematerial for Ink 1 was the same as for Comparative Ink 1, and theoligomeric curable material for Ink 2 was the same as for ComparativeInk 2. Similarly, the other components of Ink 1 and Comparative Ink 1were the same, and the other components of Ink 2 and Comparative Ink 2were the same.

3D articles were printed, layer by layer, with Inks 1 and 2 andComparative Inks 1 and 2, using an SLA printing system. After each layerof the 3D articles was provided, each layer was partially cured using aXe arc lamp prior to provision of the next layer. After all layers ofthe 3D articles were provided, the articles were post-cured using a Hglamp. Particularly, post-curing involved 10 two-minute long exposuresusing the Hg lamp.

Mechanical properties of the 3D printed articles formed from Inks 1 and2 and Comparative Inks 1 and 2 were measured as follows, and the resultsare recorded in Table II. Elongation at break was measured according toASTM D638; tensile strength was measured according to ASTM D638; tensilemodulus was measured according to ASTM D638; impact resistance (notched)was measured according to ASTM D256; and flexural modulus was measuredaccording to ASTM D790.

TABLE II Viscosity and Mechanical Properties. Viscosity Tensile TensileImpact @30° C. Strength Modulus Elongation Resistance Flexual Modulus(cP) (MPa) (MPa) (% Break) (ft · lb/in) (MPa) Ink 1 400 46.36 2005.1731.25 1.37 2157 Ink 2 — 66.92 2777.59 18.60 1.02 2791 Comparative Ink 13500 41.34 1836.21 21.82 0.99 2068 Comparative Ink 2 — 39.1 1600 14.70.60 2085

In addition to Inks 1, 2, 3, and 4 above, other inks according to thepresent invention are provided using the amounts in Table III below. Theamounts in Table III refer to the wt. % of each component of theidentified ink, based on the total weight of the ink. Additionally, “PI”stands for “photoinitiator.”

TABLE III Ink Components. Additional Oligomeric CyclopolymerizableMonomeric Curable Stabilizer/ Monomer Curable Material MaterialInhibitor Colorant PI 10-70 0-70 10-80 0.01-1 0-2 0-5 10-70 0-70 10-700.01-1 0-2 0-5 10-60 10-60  10-60  0.1-2 0.1-2   0-5 20-70 0-60 20-800.01-2 0-2 0-5 20-70 0-60 20-70 0.01-2 0.1-1   0-5 20-60 0-40 20-700.01-0.2   0-0.5 1-5 20-50 0-40 30-70 0.01-0.1 0.1-1.5 1-5 20-50 10-40 30-70 0.01-0.5 0-2 1-5 20-45 0-40 30-80 0.01-1.5 0-2 0-5 20-40 0-4030-65 0.01-1   0-1.5 1-5 20-40 10-40  30-65 0.05-1.5 0.01-1   1-5 30-400-40 30-65 0.01-2   0-0.5 1-5 30-40 10-40  30-65 0.01-0.2 0.5-1.5 1-5

All patent documents referred to herein are incorporated by reference intheir entireties. Various embodiments of the invention have beendescribed in fulfillment of the various objectives of the invention. Itshould be recognized that these embodiments are merely illustrative ofthe principles of the present invention. Numerous modifications andadaptations thereof will be readily apparent to those skilled in the artwithout departing from the spirit and scope of the invention.

That which is claimed:
 1. An ink for use in a three-dimensional printingsystem comprising: 10-70 wt. % cyclopolymerizable monomer, based on thetotal weight of the ink, wherein the cyclopolymerizable monomercomprises an acrylate moiety and an ethenyl or ethynyl moiety, andwherein the α-carbon of the acrylate moiety and the α-carbon of theethenyl or ethynyl moiety have a 1,5-, 1,6-, 1,7-, or 1,8-relationship.2. The ink of claim 1, wherein the cyclopolymerizable monomer is presentin the ink in an amount of 20-40 wt. %, based on the total weight of theink.
 3. The ink of claim 1, wherein the α-carbon of the acrylate moietyand the α-carbon of the ethenyl or ethynyl moiety have a1,5-relationship.
 4. The ink of claim 1, wherein the α-carbon of theacrylate moiety and the α-carbon of the ethenyl or ethynyl moiety have a1,6-relationship.
 5. The ink of claim 1, wherein the α-carbon of theacrylate moiety and the α-carbon of the ethenyl or ethynyl moiety have a1,7-relationship.
 6. The ink of claim 1, wherein the α-carbon of theacrylate moiety and the α-carbon of the ethenyl or ethynyl moiety have a1,8-relationship.
 7. The ink of claim 1, wherein the cyclopolymerizablemonomer has the structure of Formula (I):

wherein X is O, S, NH, NR₅, or CR₅R₆; R₁ is H or a hydrocarbon grouphaving 1-10 carbon atoms; R₂ is a hydrocarbon group having 1-4 carbonatoms; R₃ is a hydrocarbon group having 1-4 carbon atoms; R₄ is HC═CH₂or C≡CH; R₅ is a hydrocarbon group having 1-4 carbon atoms; R₆ is ahydrocarbon group having 1-4 carbon atoms; and the total number ofcarbon atoms of R₂ and R₃ does not exceed
 5. 8. The ink of claim 7,wherein X is O.
 9. The ink of claim 7, wherein X is S.
 10. The ink ofclaim 7, wherein X is NH or NR₅.
 11. The ink of claim 7, wherein X isCR₅R₆.
 12. The ink of claim 7, wherein the total number of carbon atomsof R₂ and R₃ does not exceed
 4. 13. The ink of claim 7, wherein thetotal number of carbon atoms of R₂ and R₃ does not exceed
 3. 14. The inkof claim 7, wherein the total number of carbon atoms of R₂ and R₃ is 2.15. The ink of claim 7, wherein the cyclopolymerizable monomer has thestructure of Formula (II):


16. The ink of claim 1, further comprising: 10-80 wt. % oligomericcurable material; and up to 80 wt. % additional monomeric curablematerial, based on the total weight of the ink.
 17. The ink of claim 1,further comprising at least one photoinitiator, at least one colorant,or one or more additives selected from the group consisting ofinhibitors and stabilizing agents.
 18. A method of printing athree-dimensional article comprising: selectively depositing layers ofan ink in a fluid state onto a substrate to form the three-dimensionalarticle, wherein the ink comprises the ink of claim
 1. 19. The method ofclaim 18 further comprising: partially curing the ink prior tocompletion of deposition of all layers of the ink; and post-curing theink following completion of deposition of all layers of the ink, whereinpartially curing the ink primarily comprises polymerizingacrylate-containing species of the ink via acrylate polymerization; andwherein post-curing the ink primarily comprises cyclopolymerizing theacrylate moiety and the ethenyl or ethynyl moiety of the monomer.
 20. Amethod of printing a three-dimensional article comprising: retaining anink in a fluid state in a container; selectively applying energy to theink in the container to solidify at least a portion of a first fluidlayer of the ink, thereby forming a first solidified layer that definesa first cross-section of the article; raising or lowering the firstsolidified layer to provide a second fluid layer of the ink at a surfaceof the fluid ink in the container; and selectively applying energy tothe ink in the container to solidify at least a portion of the secondfluid layer of the ink, thereby forming a second solidified layer thatdefines a second cross-section of the article, the first cross-sectionand the second cross-section being bonded to one another in az-direction, wherein the ink comprises the ink of claim 1.